Earth maps: NASA Visible Earth / Earth Observatory, Blue Marble and Earth at Night.
https://eoimages.gsfc.nasa.gov/images/imagerecords/57000/57730/land_ocean_ice_2048.jpg
https://eoimages.gsfc.nasa.gov/images/imagerecords/55000/55167/earth_lights_lrg.jpg
NASA media usage guidelines: https://www.nasa.gov/nasa-brand-center/images-and-media/
NASA imagery used for visualization; no NASA endorsement is implied.
Three.js 0.180.0: MIT; see ../vendor/THREE-LICENSE.txt. Core import suffix adjusted for local module serving.

Natural Earth update: day, cloud and ocean-reflection maps from the official Three.js r180 example assets.
https://github.com/mrdoob/three.js/tree/r180/examples/textures/planets
Source files: earth_day_4096.jpg, earth_clouds_1024.png, earth_specular_2048.jpg.
Local filenames: earth-natural-day.jpg, earth-natural-clouds.png, earth-natural-ocean.jpg.

Earth day and combined terrain/cloud imagery by Solar System Scope (INOVE), via Three.js r180 examples.
https://www.solarsystemscope.com/textures/
CC BY 4.0: https://creativecommons.org/licenses/by/4.0/
Adaptations: lighting, cloud-layer animation and terrain shading applied at runtime; source files locally renamed.